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2011-2014 Mustangs
Exhaust
Long tube headers, which Primary size is 'best'?
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<blockquote data-quote="assasinator" data-source="post: 15455012" data-attributes="member: 105188"><p>sorry to say it man, but your header 'theory' is wrong in every way. </p><p></p><p>diameter, length and collector dimension determine rpm band.</p><p></p><p>i dont know where to start. </p><p></p><p>first, it is always possible to go with too large of a primary tube, but that overkill is determined by exhaust gas flow in pounds per minute. </p><p></p><p>if you have two engines....a 400 inch big block making 600 crank hp is going to like the same basic primary tube as a small block making 600hp.</p><p></p><p>where there is a difference is rpm tuning exhaust pulses for a supersonic low pressure wave to arrive at the exhaust valve as it is opening. </p><p></p><p>a big engine needs a longer lol tube to slow the arrival of the pulse for lower rpm operation. a small high rpm engine needs shorter primary tubes for a faster arriving pulse. </p><p></p><p>the tube diameter can change for tuning. a smaller tube shortens the primary length required for pulse arrival at the same rpm.</p><p></p><p></p><p>it takes too long to explain everything, but simple adding tubing area has nothing to do with primary tube effectiveness. </p><p></p><p>there is a venturi effect of primary tubing from exhaust gas inertia also. too large of a tube for the exhaust gas volume negates that advantage. THAT and rpm tuning are the reason a particular tube can be too large. </p><p></p><p>and every change in diameter a tube makes send a pulse down the exhaust and back to the valve. THAT is why stepper headers work. they allow multiple rpm sweet spots for diameter changing pulses. </p><p></p><p>that is about one percent of header theory.</p></blockquote><p></p>
[QUOTE="assasinator, post: 15455012, member: 105188"] sorry to say it man, but your header 'theory' is wrong in every way. diameter, length and collector dimension determine rpm band. i dont know where to start. first, it is always possible to go with too large of a primary tube, but that overkill is determined by exhaust gas flow in pounds per minute. if you have two engines....a 400 inch big block making 600 crank hp is going to like the same basic primary tube as a small block making 600hp. where there is a difference is rpm tuning exhaust pulses for a supersonic low pressure wave to arrive at the exhaust valve as it is opening. a big engine needs a longer lol tube to slow the arrival of the pulse for lower rpm operation. a small high rpm engine needs shorter primary tubes for a faster arriving pulse. the tube diameter can change for tuning. a smaller tube shortens the primary length required for pulse arrival at the same rpm. it takes too long to explain everything, but simple adding tubing area has nothing to do with primary tube effectiveness. there is a venturi effect of primary tubing from exhaust gas inertia also. too large of a tube for the exhaust gas volume negates that advantage. THAT and rpm tuning are the reason a particular tube can be too large. and every change in diameter a tube makes send a pulse down the exhaust and back to the valve. THAT is why stepper headers work. they allow multiple rpm sweet spots for diameter changing pulses. that is about one percent of header theory. [/QUOTE]
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Long tube headers, which Primary size is 'best'?
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